Currently a pxe-client has to contact with ironic-api through
it's internal endpoint during lookup() period.
However, the pxe-client cannot access kube-dns by ifself,
so it needs additional dns server. (or Using NodePort)
With additional dns server, it will be safer for pxe-client
to contact with ironic-api through it's public endpoint(passing by ingress)
rather than internal endpoint directly becuase internal pod's IPs would be changed frequently.
Also, I refered to {Values.conf.ironic.glance.swift_endpoint_url}.
(swift is also accessed by the pxe-client and swift_url's default is public endpoint)
Change-Id: I0ad97f3ed608973d7e5a4a11d87595fe258a0db5
65bd9a7a04